Interrupt handler

Code entered to handle an interrupt. It identifies and acknowledges relevant device state and arranges service, possibly deferring work. The Linux kernel's generic flow layer and device driver callback have distinct responsibilities. ^[ref]

When several devices share an interrupt, the handler examines each device's pending status and acknowledges every active source. Separate tests allow simultaneous requests to be serviced. A source becoming pending during the scan must cause another interrupt or be found by a justified rescan; the necessary behaviour depends on the interrupt controller and device protocol.